This invention relates to a sewing machine in general, and particularly to an electronic sewing machine capable of proportionally enlarging or reducing the size of a stitch pattern selected from a plurality of stitch patterns stored in an electronic memory of the sewing machine.
In a conventional electronic sewing machine there is provided an electronic memory which stores a plurality of data for controlling the needle lateral amplitude and the fabric feed amount in such manner that the respective stitch patterns may be produced in the maximum size. In actual stitching operation, the selected stitch pattern is automatically reduced to be of an optimum size by the reduction rate data memorized in an auto-data memory. However, there may arise some occasions that the sewing machine operator is required to stitch a pattern of a size different from the automatically controlled size. For example, it may be possible that the operator wishes to produce a floral pattern design, one of the stitch patterns stored in the memory, but the automatically controlled size (shown in FIG. 1 as pattern A) is somewhat larger than that (shown in FIG. 1 as pattern B) he desires to stitch. In order to produce such a proportionally enlarged or reduced pattern design, the needle lateral amplitude and the feed amount must be enlarged or reduced with the same and common rate with respect to the automatically controlled size thereof. However, the manual adjusting system for the needle amplitude and for the fabric feeding amount have been separated from each other and therefore must be operated independently. This has made it difficult to obtain a proportionally enlarged or reduced stitch pattern design.